1. Field of the Invention
The present invention relates to a video signal recording apparatus, and more particularly, to an apparatus for picking up a video signal recorded on a recording medium and copying a frequency modulated (FM) signal without demodulation. The present invention is based on Korean Patent Application No. 96-33269, which is incorporated herein by reference.
2. Description of the Related Arts
Copying a video signal recorded on a video tape is generally carried out as follows.
A VCR on a reproducing side first picks up a modulated and recorded video signal, compensates the amplitude and frequency characteristics of the picked-up video signal using a pre-amplifier and an equalizer, and demodulates the frequency characteristics compensated modulated video signal and outputs the result. A VCR on a recording side then receives the demodulated video signal output by the VCR on the reproducing side, compensates the frequency characteristics of the received demodulated video signal, modulates the frequency characteristics compensated demodulated video signal again, and then records the result on a tape through a video head via a recording amplifier.
Copying the modulated video signal without demodulating it has-recently become possible. According to a recent technique of directly copying a modulated video signal, noise can be reduced and the number of component parts decreased, compared with a conventional video copying technique.
FIG. 3 is a block diagram showing the configuration of a conventional video signal copying apparatus. FIGS. 4A through 4D show the frequency characteristics of signals in the conventional apparatus shown in FIG. 3.
A recent video signal copying apparatus will be now briefly be described, referring to FIGS. 3 and 4A through 4D.
A modulated video signal picked up from a tape by a video head has a color signal (LC) and a luminance signal (YFM) as shown in FIG. 4A. However, since the signal processing procedures for the luminance and color signals are different from each other, the signals are separated by a high-pass filter 301 and a low-pass filter 306. The output signal of the high-pass filter 301, including only the frequency modulated luminance signal (YFM) as shown in FIG. 4B, is converted into a recording luminance signal by a phase corrector 302 for correcting the delay time and the phase, compensated by an FM signal equalizer 303 for compensating frequency characteristics, limited by a double limiter 304 for preventing black-and-white inversion, and corrected and amplified by a first recording equalizer 305 for correcting recording frequency characteristics and amplifying the frequency-corrected recording signal.
The output signal of the low-pass filter 306, being a low frequency converted color signal (LC) as shown in FIG. 4C, is amplified to a predetermined level by a voltage control amplifier 307, and then converted into a recording color signal by a second recording equalizer 308 for correcting frequency characteristics and amplifying the frequency-corrected signal.
Thereafter, the recording luminance and color signals are mixed by a mixer 313, and the mixed output signal is recorded on a tape by a video head as a signal having the frequency characteristic shown in FIG. 4D.
However, black-and-white inversion may occur when a signal is processed, even in the above-described recent copying technique of directly recording a modulated video signal without demodulation. That is, a large-amplitude but low-frequency component and a small-amplitude but high-frequency component are mixed in an FM luminance signal. However, the frequency component having a small amplitude, being an FM carrier of a white clip, does not cross the zero reference level of a limiter while passing through the limiter circuit, so that a portion of a carrier signal may not be output. Accordingly, when a limited signal is demodulated, a portion of the carrier at a white clip portion of the FM carrier signal is lost, resulting in black-and-white inversion.
Also, according to a recent conventional modulated video signal recording apparatus, a filter for separating the low frequency converted color signal from the demodulated video signal has a narrow frequency band, so that its delay time is increased due to the characteristics of the filter.
Accordingly, a delay correcting circuit for correcting a difference in delay time of a filter is required for processing the separated FM luminance signal. Also, the number of component parts increases, and the signal characteristics are deteriorated by the delay correcting circuit.